The present invention relates to a method for recharging an electrical energy storage device of a hybrid vehicle, the hybrid vehicle including an internal combustion engine, a first electric machine, a second electric machine, and a drive shaft, the internal combustion engine and the first electric machine being directly mechanically coupled, the second electric machine and the drive shaft being directly mechanically coupled, and the internal combustion engine and the drive shaft being variably mechanically coupled by a gear device. Moreover, the present invention relates to a drive unit for a hybrid vehicle, including an electrical energy storage device, an internal combustion engine, a first electric machine, a second electric machine, and a drive shaft, the internal combustion engine and the first electric machine being directly mechanically coupled, the second electric machine and the drive shaft being directly mechanically coupled, and the internal combustion engine and the drive shaft being variably mechanically coupled by a gear device, and a hybrid vehicle that includes a drive unit.
It is known in recent automotive technology to design the vehicles as hybrid vehicles, and to use an internal combustion engine as well as at least one electric machine for the drive of the vehicle. The at least one electric machine may generally be operated as a motor and also as a generator. This type of hybrid vehicle may typically be driven either solely by the internal combustion engine, solely by the at least one electric machine, or by the internal combustion engine and the at least one electric machine together. Two electric machines are often used in recent hybrid vehicles, a first electric machine generally being directly mechanically coupled to the internal combustion engine, for example via a belt drive and/or a switchable belt pulley. In contrast, the second electric machine is often directly coupled to a drive shaft of the hybrid vehicle.
In addition, in hybrid vehicles it is known to recharge an electrical energy storage device, which supplies the electric machines of the hybrid vehicle with electrical energy, during operation of the hybrid vehicle. For this purpose, the electric machines may be operated as generators. In addition to a recuperation mode, in which mechanical kinetic energy of the hybrid vehicle is converted into electrical energy by one of the electric machines, it is also known to drive an electric machine by the internal combustion engine, with the electric machine as a generator converting this mechanical drive energy into electrical energy (see DE 10 2008 060 954 A1, for example). This type of drive of two electric machines by the internal combustion engine in order to generate electrical energy is also basically known (see WO 2014/090704 A1, for example). A control and regulation of an operation of the electric machines, for example with regard to a preferably low loss in the electrical supply to the electric machines and/or an overall torque to be generated, may take place (see DE 10 2013 221 814 A1, for example). However, it is often not possible to provide an optimal recharging of the electrical energy storage device, in particular a particularly energy-efficient and low-loss charging of the electrical energy storage device, in known hybrid vehicles.
The object of the present invention, therefore, is to at least partially eliminate the above-described disadvantages in methods for recharging an electrical energy storage device of a hybrid vehicle, in drive units for a hybrid vehicle, and in hybrid vehicles. The object of the present invention in particular is to provide a method for recharging an electrical energy storage device of a hybrid vehicle, a drive unit for a hybrid vehicle, and a hybrid vehicle, which easily and cost-effectively allow a particularly energy-efficient and low-loss recharging of the electrical energy storage device, in particular the electrical energy to be generated being distributed to two electric machines in an optimized manner.